The effect of explosive mixtures upon impact sensitivity.

Villi EFFECT Of EXPLOSIVE MIXTURES
UPON IMPACT SENSITIVITY

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The Effect

of

Explosive Mixtures

upon
Impact Sensitivity

8854

on spine:

SINCLAIR
1956

S536

Letter on front cover:

E EFFECT CF EXPL MIXTUI
UPCN IMPACT SENSITIVITY

James E. Sinclc

The Effect

of

Explosive Mixtures

upon
Impact Sensitivity

by

James E. Sinclair
Assistant Professor of Chemistry

Submitted in partial fulfillment
of the requirements
for the degree of

MASTER OF SCIENCE
IN
CHEMISTRY

United States Naval Postgraduate School
Monterey, California

19 5 6

Si

This work is accepted as fulfilling

the thesis requirements for the degree of

MASTER OF SCIENCE

IN

CHEMISTRY

from the
United States Naval Postgraduate School

PREFACE

The testing of explosives has always contained a certain element of
unreliability which is due to their natural unpredictability. This has
led workers in the laboratory and in the field to overdesign from the
standpoints of both desired power and desired sensitivity. Overdesign
has in most cases proven practical and is prevalent throughout the entire
industry.

However in investigating the fundamental properties of explosives,
parameters are desired that are as exact as possible. This is difficult
in a medium that is relatively unpredictable and special technique must
be used in order to evaluate the results of explosive tests.

The purpose of this paper is to show one method by which impact
sensitivity may be used, not only to evaluate a particular explosive as
to methods of use, storage, and handling, but also to explore the proper-
ties that affect the impact sensitivity. Therefore an explosive system
was investigated as to the effect of varying mixtures of two components
upon the impact sensitivity. The method used in this report is largely
the result of collaboration with Mr. William Guy and R. Eli Besser of
the Naval Ordnance Test Station. As the project progressed however,
changes were made in the apparatus and in the testing procedure.

The writer wishes to thank Professor Gilbert F. Kinney who suggested
the problem originally and has always been interested, helpful and
encouraging.

ii

TABLE OF CONTENTS

Item

CERTIFICATE OF APPROVAL

PREFACE

TABLE OF CONTENTS

LIST OF ILLUSTRATIONS

CHAPTER I

II

III

IV

V
BIBLIOGRAPHY
APPENDIX

Title

Introduction
The Apparatus

Experimental Procedure

1. Preparation of Samples

2. Testing Procedure

The Statistical Approach
Experimental Results

Page

i

ii

iii

iv

1

4

8

13
21
29
30

iii

LIST OF ILLUSTRATIONS

Figure Title Page

1 Photograph of Impacter 5

2 Diagram of Impacter Assembly 7

3 Chart of Run No. 3 16

4 Plot of Run No. 3 16

5 Chart of Run No. 3 (No assumed points) 18

6 Plot of Run No. 3 (No assumed points) 18

7 Probability Plot of Run No. 3 19

8 Plot of Amount versus Sensitivity of TNB 22

9 Plot of Amount versus Sensitivity of TNT 23

10 Plot of TNB-Chalk Mixtures versus Sensitivity 25

11 Plot of TNT-Chalk Mixtures versus Sensitivity 26

12 Plot of TNB-TNT Mixtures versus Sensitivity 27

13 Photograph of Ro-Tap Machine 31

14 Photograph of Atlas Powder Measure and Fisher-
Kendall Mixer 32

15 Chart of Run No. 2 33

16 Probability Plot of Run No. 2 34

17 Chart of Run No. 8 35

18 Probability Plot of Run No. 8 36

19 Sunmary Chart of Project 37

iv

INTRODUCTION

The impact sensitivity of an explosive is usually considered today
in the same manner as in the earliest experiments, namely, "The explosive
must be as insensitive as possible and still explode when and where
desired". This is not difficult since explosives such as trinitrotoluene
(TNT) and trinitrobenzene (TNB) are available, which are extremely diffi-
cult to initiate without the aid of an explosive train or blasting cap and
yet are easily "set off" with these aids.

The difficulty encountered in using explosives is that a certain
number of explosions, due to impact alone, occur without normal cause.
Many examples of unusual explosions occurred during World War II. In one
incident, a 500 pound bomb loaded with TNT, but without the fuse or initia-
tor attached, was dropped approximately one foot and exploded. Normally,
one would expect such a bomb to be completely insensitive to this type of
shock. In fact, many similar bombs did not explode even with fuses and
initiators, when dropped in bombing raids. This property of explosives
is well known and in evaluating impact sensitivity, one must take this
unreliability into account since it exists in all explosives and no method
has been found to eliminate it .

The most logical approach to a problem of this kind lies in the realm
of statistics. The probability of an explosion occurring under strictly
controlled conditions may be expressed by a statistical number obtained
by a large sampling of data. Under these conditions the pertinent point
is not where the explosion occurs all the time or where it never occurs,
but at some selected value, say fifty percent of the time. This concept
provides for a logical comparison of different impact sensitivities.

1

Therefore, if a machine can be set up to impact successive samples of
an explosive, with an infinite number of varying impacts, over an infinite
number of samples, this answer would be forthcoming. This method is imprac-
tical because the information gained is not proportional to the effort
expended.

One method which has been used in practice, is to drop a weight on an
explosive sample from one height for 100 times. This is repeated at dif-
ferent heights such that the height range extends from the height at which
it explodes 90$ of the time to that at which it explodes 10$ of the time.
This method gives good results in that it reports percent explosion as a
function of drop height and reproduction of results is fairly good. The
difficulty in the above method is that it is long and tedious and because
of this few comparative results are available.

Another and more practical approach to the problem is the method used
at the Naval Ordnance Test Station. This method, which was similar to the
"Bruceton" method, consists of a series of tests, perhaps 20, in which the
sequence of tests is carried out in a precise manner. Here, a weight is
dropped upon a fixed quantity of explosive and if an explosion occurs,
the weight is dropped from a height a fixed distance lower for the next
test. If there is no explosion, the weight is dropped from a height the
same fixed distance higher for the next test. Thus the impact is changed
for every test and in a precise and organized manner. Statistical methods
are used to interpret the test results.

The "Naval Ordnance Test Station" method also specifies the handling

of variables, such as the ratio of hammer weight to sample weight and the

nature of the impacting surfaces. In general, this method seems the most
practical and was adopted with certain modifications for this investigation.

Because of the unreliability of impact sensitivity results, few investi-
gations have been carried out on anything but pure explosives and melted
mixtures thereof. Explosives which were either immiscible or not practical
to melt have not been well studied.

Trinitrobenzene (TNB) and trinitrotoluene (TNT) are examples of explo-
sives which are not practical to melt together because, although their
chemical structures are very similar, differing only by one methyl group,
their melting points and other properties differ considerably. For this
investigation it was necessary to mix them together physically to study
the impact sensitivity of various mixtures. It is hoped that these results
will add to the general knowledge of explosives and perhaps throw some
light upon the problem of impact sensitivity testing.

THE APPARATUS

An impact tester is essentially a machine which drops a fixed weight
through a fixed distance. The important consideration is the production
of reproducible impacts. There are many different types: some drop a ball
shaped weight, some drop a weight that is on a hinged arm, and some drop
along a vertical track. The machine in which the hammer drops along a
vertical track seems to be the mose rugged and is used in this project.

The impacter (See Fig. 1) is a steel tower with a geared motor at the
top which raises and lowers a carriage containing two magnets. One magnet
holds the impacter hammer so that there is no mechanical connection to
hinder its free fall. The other magnet operates a pin that prevents the
hammer from falling accidentally. Since the hammer weighs 2.2 kilograms
(5 pounds) and can fall from a height of 150 centimeters, this precaution
is necessary. The hammer slides on lubricated vertical tracks with prac-
tically no friction. Electrical switches are operated automatically so
that the hammer rises to a preset height, falls and is picked up again by
the throwing of one switch. The sliding hammer falls upon a steel cylin-
der known as a "floating" hanmer and weighs approximately 85 grams. The
floating hammer rests upon the explosive being tested. The explosive
rests upon a half inch square of special garnet paper which is on a steel
anvil. The assembly is contained in a steel cup which* like the entire
machine is removable. The cup is enclosed by a steel cylinder called the
"nest". The "nest" is warmed to 100° F by brazed copper coils fed with
water from a thermally regulated both in the base of the impacter. The
cup and the nest contain a hole in their respective bottoms through which

Fig.l The Impacter
5

an externally operated plunger can raise or lower the anvil to load and
unload the charge. (See Fig. 2).

The advantages of the confinement of the explosive in the steel cup
are: (l) Temperature control is more easily achieved, and (2) No special
safety precautions are necessary beyond wearing a face shield.

The amount of explosive material used for a test is conveniently
metered by means of a commercial powder measure which is mounted near
the impacter. Since the powder measure delivers by volume, it must be
calibrated for each different explosive or mixture. The measure is
designed for larger volumes than needed for a single series of tests so
a molded polyethylene plug is used to occupy the excess volume.

The mixtures of explosives are prepared by grinding, screening, and
dry mixing. For the grinding operation, a standard Ro-Tap machine was
used. The particle size of the explosive was determined by standard
"Tyler" screens, and the dry mixing was done by a "Fisher Kendall" mixer,
(See Appendix).

With the exception of the impacter, all equipment used was standard
laboratory gear.

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EXPERIMENTAL PROCEDURE

1. Preparation of Samples

I, 3, 5-trinitrobenzene and 2, A, 6- trinitrotoluene were obtained
from "Eastman Organic Chamicals". Chalk, prepared powder U3P, was obtained
from Eimer and Amend Division of Fisher Scientific Company. The samples
were prepared by grinding in the following manner.

The pure material was placed on a number 70 "Tyler" screen with five
copper discs the size of a penny. Underneath was a number 120 screen
also containing five discs and beneath that a number 140 screen with no
discs. The bottom of the screen assembly was a solid or "thru" pan.

The screen assembly was placed in the'Tto-Tap" and shaken until all
the material had passed through the number 120 screen. The material pass-
ing through the number 140 screen was rejected. Therefore the size of
the particles of the material used was small enough to pass through the
120 screen with a 125 micron opening but too large to pass through the
140 screen with a 105 micron opening. This size was selected because of
screening convenience and also for ease of mixing since the particles
would "flow" easily in the "tumbling" operation of mixing.

The grinding and sizing procedure used here was selected after other
methods had been tried. The use of either a ball mill or mortar and pestle
with subsequent screening is quite dangerous in that clouds of fine dust
are raised which are not only explosive but highly toxic both internally
and externally. In addition, a considerable static charge is accumulated
by the movement of the explosive in non-metallic media so that a sparking
hazard exists.

8

The grinding on the brass and copper screens in the "Ro-Tap" still
raised dust and accumulated a static charge but after a fexv minutes the
dust settled and the charge disappeared due to the conducting nature of
the apparatus. In this manner, the finely divided material was handled
the minimum number of times both safely and easily.

In tests involving the pure material no further preparation was used.
Whenever it was desired to mix materials, the powders were weighed on an
analytical balance in the proper proportion; placed in vials with ground
glass stoppers and mixed in a "Fisher Kendall" mixer. The action involved
is a continuous rotation of the container with a simultaneous rocking
motion through an angle of ninety degrees, which, according to the manu-
facturer, should give a uniform distribution in five minutes mixing time.
Since mixing time did not hinder other phases of the project, all samples
were mixed for 30 minutes and no lack of uniformity was detected. After
mixing, the samples were allowed to stand for twenty-four hours to allow
them to discharge any accumulated static charge.

2. Testing Procedure

The prepared samples were placed in an "Ideal" powder measure which
was adjusted to "throw" the desired amount of material. The measure was
adjusted until the amount thrown was within plus or minus one milligram.

The measured sample fell from the powder measure upon the rough sur-
face of a half inch square of 180 grit, 5WD43 grade, garnet paper manu-
factured by the Carborumdum Company, in a rough cone shape. The garnet
paper containing the coned material was placed on the anvil (See Fig. 2),
which was raised from the cup to receive it, with the explosive side

upward. The anvil containing the charge was lowered into the cup and a
strip of white paper, long enough to go all the way around the cup and
approximately one half inch in width, was placed in the cup. The float-
ing hammer was then placed in the cup.

The floating hammer pushed the paper down until it formed a ring
around the cup, one half inch from the charge. Another action of the
floating hammer was to flatten the charge until a circle approximately
three eighths of an inch in diameter was formed. The size of the circle
was reasonably uniform as to diameter and varied with the size of the
charge in thickness only. The meter stick which measured the drop height
was adjusted for each series of tests because the thickness of the sam-
ple varied, and the impacting surfaces were ground smooth for each run
of approximately 25 individual tests, thereby making adjustment necessary
for each run.

After each test, the floating hammer was lifted manually and the
white paper examined. If the charge had fired, the paper was blackened
and this was used as the criterion of explosion. This technique was
found to be necessary as other indications were often misleading. At
first the criterion of a blackening of the sandpaper was used. When
results were obtained which seemed improbable, sugar was substituted for
the explosive. The sandpaper was blackened by the sugar when impacted.
Since sugar cannot explode, this effect necessitated a change in the
method of detection.

The use of paper to detect explosions in this method still requires
care and skill, for in many cases bits of garnet paper are pushed through
the white indicating paper which is subsequently discolored without any

10

evidence of explosion. Therefore some judgment must be exercised in examin-
ing the paper.

The falling hammer is dropped automatically from pre-set heights on
the floating hammer. In the first series of runs, a five pound falling
hammer was used. The ratio of hammer weight to sample weight, which is
two kilograms to twenty milligrams, was felt to be inapplicable here since
sample weight varied from six to sixty milligrams. In subsequent runs the
amount of charge was fixed to 23 milligrams so that the falling hammer was
adjusted to 2.3 kilograms.

Following each impact or test, the floating hammer is lifted from
the cup and placed on the side of the nest, which keeps the hammer from
cooling. Then the paper is examined, a record of the test taken, and
the height for the next impact test set. The anvil is raised from the
cup, but not removed, scraped with a scapel and blown off with com-
pressed air. The next sample is placed on the anvil, dropped down in
the cup and the indicating paper put in place. Then the floating ham-
mer is scraped, blown off and placed in the cup. This order of proce-
dure is necessary to prevent the impacting surfaces of the anvil and
floating hammer from cooling off.

After each run, the impacting surfaces of the anvil and floating
hammer are sanded smooth. The falling hammer is checked for tightness,
and the cup assembly washed with acetone to remove any unexploded
material. In experiments of this type, a certain amount of unexploded
material accumulates so that it was necessary to burn daily all fragments

11

together with the acetone washings to avoid any excessive build-up of
waste explosive. This was done in a large bucket in the fume hood with
no difficulty.

12

THE STATISTICAL APPROACH

In testing the impact sensitivity of an explosive, a hammer is
dropped from a certain height on the sample under precisely controlled
conditions. If no explosion occurs, the hammer is raised a definite
distance higher and the test repeated. If an explosion occurs, the
hammer is lowered the same distance and the test repeated. Normally
this procedure is continued for twenty-five tests and the results
analyzed.

This procedure assumes that the detection of explosion is certain
and as explained previously it is not always certain. Even with the
refinement of the indicating paper detector, some results are doubtful.
Other uncertainties, such as the height at which to start the run, how
many tests to make for one run, and when to stop a run, appear. There-
fore certain arbitrary rules had to be set up and followed to make the
tests meaningful.

The runs were all made under the following rules:

1. Every run was started at one hundred centimeters for the first
drop height. If an explosion occurred, the drop height was moved down
twenty centimeters, or if no explosion occurred the next drop height
was twenty centimeters higher. This procedure was followed until the
pattern changed. For example: explosions occurred at 100, 80 and 60
centimeters, but no explosion at 40. The next test would be at 45 centi-
meters, and the recording of the data would start. On the other hand,
assume no explosion occurred at 100 and 120 centimeters, but an explo-
sion did occur at 140 centimeters. The next test would be at 135

13

centimeters and the recording would start. This procedure was felt
necessary because it established a definite method by which the explo-
sive range could be found. When runs were repeated, this same technique
w s followed even though the range was purportedly known. The ranging
shots however were not recorded, because since they were all performed
in the same manner, the results could be obtained if necessary.

2. On those occasions, when it is difficult to judge whether or
not an explosion has occurred, the decision is arbitrarily made that the
result is the same as the previous test. The 50 percent point of the
explosive is sought in these tests so that it is more logical to inter-
pret a doubtful point in a manner so as to more quickly arrive at a point
of definite change. If a doubtful point, follows a no explosion point,
then the next test is with a higher drop height so that the probability
of an explosion is greater for this test. The reverse is also true, for
if an explosion is followed by a doubtful point, the next test with lower
drop height has a greater probability of no explosion.

The assumptions that a doubtful point is a "no explosion" , "explo-
sion" or "different from the last test" all lead to a greater possibility
of another doubtful point for the second succeeding test. The technique
of repeating a doubtful test at the same drop height would alter the
statistical pattern.

3. After twenty tests have been recorded, the run continues until
the next change, either no explosion or explosion. This provides a rule
for ending the run in a logical fashion. In the ideal run, all of the
no explosion points would be five centimeters below the explosion points
and no problem would exist.

The actual runs differ in that, there is a greater differential
between the 100$ and the 0$ points so that a doubt exists at the end of
the run as to the effect of another test. If the run stops at a change
between explosion or no explosion, it requires at least two more tests
to make any appreciable effect on the run.

These rules have been found to be helpful for they provide positive
decisions in cases where some doubt may exist.

Another concept is necessary in interpreting the data. If an explo-
sion occurred at 50 centimeters for a certain test, it is assumed that
the explosion would also have occurred at any higher point since the
impact would be greater. Also if no explosion occurred at 45 cm for
another test, it is assumed that no explosion would occur at any lower
point since the impact would be less. If the data are organized in this
fashion with drop heights vertically charted and the test numbers hori-
zontally charted, this extra information obtained by these assumptions
can be added and the percent probability for explosion at any height
ascertained.

This method is illustrated in Figure 3 with "E" representing an
actual explosion and "N" representing an actual no explosion. The assumed
explosions are represented be "e" and the assumed no explosions by "n".
From this illustration the height at which the percent probability of
explosion is 50$ can be obtained. This can be seen to be 63 centimeters
by plotting drop height versus percent explosion. (See Fig. 4). The
assumed points have aided the test results in that the number of tests
considered is 79, instead of 22 and the assumed points are probably as
accurate as the actual points.

15

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The value of the assumed points can be further demonstrated by
Figure 5. On this chart, the tests of Figure 3 have been repeated and
no assumed points added. The data obtained are contradictory and rela-
tively useless, while the resulting curve Figure 6 is impossible. Thus
in order to obtain usable results, the method must contain the "assumed
point" concept.

An additional refinement is used in this report. The percent proba-
bility is plotted versus drop height on probability paper instead of nor-
mal rectangular graph paper. This enables one to draw the best straight
line through the plotted points and obtain the $0% point (See Fig. 7).
The result does not differ significantly in the 50$ point being 65
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The main advantage of the probability paper is that the slope of
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seen. This deviation is in the form of an "S" shaped curve when plotted
on probability paper.

The best straight line method is used here since the deviation from
the normal probability is slight and the observed standard deviation can
be expressed as the number of centimeters between the fifty percent
point (FPP) and the%83.3 percent point. The run can then be described
by the FPP and the OSD expressing both the sensitivity and the expected
variability.

However as stated in the introduction, it is felt that a commen-
surate return should be expected for any number of tests, and the number

17

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of tests per run, about twenty five, is a reasonable mean between the
existing extremes of extremely accurate points and the length of time
involved in making one run, which is approximately two hours.

20

EXPERIMENTAL PROCEDURE

Before comparing the impact sensitivities of explosive mixtures
an investigation was made upon the sensitivity of varying amounts of
material. The discovery was made that there is a most sensitive amount
of an explosive. This has not been reported in the literature and is
considered to be an important contribution.

The most sensitive amount of both TNB and TNT is approximately
23+ 1 milligrams. The lower amounts are less sensitive because the
explosive layer is thinner and since it is spread on garnet paper, the
garnet grains are large enough to absorb an appreciable part of the
shock. The greater amounts are also less sensitive, but this is due to
a dilution factor. The impact is divided among more particles of explo-
sive, making less the probability of any one particle absorbing enough
energy to explode.

This could perhaps be thought of as the energy to cause explosion
by impact expressed in calories per mol. This energy for pure TNT is
30+ .5 kilocalories per gram mol as computed for the 50$ point while
the energy of activation for TNT calculated from curves in reference 4
was approximately 38.3 kilocalories per gram mol. These results are of
the same order of magnitude and if the 100$ point was used in the cal-
culation for the energy of impact instead of the 50$ point, the calcu-
lated energy would be 34.5+ »5 kilocalories per gram mol.

After the most sensitive amounts of the two explosives had been
found, (See Figs. S and 9), the influence of large amounts of foreign
was investigated. Runs were made on mixtures of chalk with each

21

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explosive. In these tests, the amount of mixture used for each test was
determined by the most sensitive amount of material found in the pre-
vious series of runs. This was 23 milligrams, so the tests were all
made using this amount of mixture.

The results from the second series of runs (See Figs. 10 and 11),
were of the nature of dilution alone, that is the sensitivity decreased
in a reasonable manner up to the highest point of drop height available.
An interesting facet of these results was that the TNB apparently is
more affected by dilution than the TNT.

The third series of tests in which TNB and TNT were mixed and the
mixture sensitivity studied show an interesting trend. The sensitivity
of the mixture is above that of the TNT until 15% of the material is TNB
(See Fig. 12). In no case did the sensitivity of the mixture become
lower than that of the TNB. This shows that the effect of the TNB upon
the TNT and vice versa is considerably more than dilution.

This curve exhibits the same characteristics as some melting point
curves in which a eutectic is formed. The explanation may be found in
considering it from the viewpoint of Bowden and Yoffe (Ref. 1). In
their investigation, evidence of the thermal effect of impact as the
initiating agent was brought out. The presence of hot spots, formed
under these conditions seems likely as do the explosions resulting from
them.

A possible explanation of the increasing sensitivity of the TNB-
TNT mixture probably lies in the fact that the melting point of the
mixture is lowered in a similar fashion. Since the hot spot formation
will be in a material of lower melting point, the temperature rise

24

140

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versus

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should take place more rapidly because less energy is required to reach
the melting point of this material. Correspondingly there will be a
greater amount of energy available for the liquid.

28

BIBLIOGRAPHY

1. Bowden, F.P. and
Yoffe, A.D.

Initiation and Growth of Explosion in
Liquids and Solids, Cambridge University-
Press (1952)

2. Davis, T.L.

3. Clift, G.D. and
Fedoroff, B.T.

4. Robinson, C.S.

5. O'hart, T.C.

6. Eyring, H., Powell, R.E.
Duffy, G.H. and
Parlin, R.B.

The Chemistry of Powder and Explosives,
Wiley & Sons, Inc. (1943)

Explosive Compounds and Allied Substances,
Lefax Soc, Inc. (1943)

Explosions, Their Anatomy and Destruc-
tiveness, McGraw-Hill (1944)

Elements of Ammunition, Wiley & Sons, Inc.
(1946)

The Stability of Detonation, Chemical
Reviews, (Aug. 1949)

29

APPENDIX

The auxilliary equipment is pictured in figure 13 (The Ro-Tap
Machine) and Figure Ik (The Altos Powder Measure and the Fisher-Kendall
Mixer).

Two typical runs have been included. Figure 15 is a chart of a
typical high O.S.D. (Observed Standard Deviation) run with its proba-
bility plot on Figure 16. Figure 17 is a chart of a typical low O.S.D
run with its probability plot on Figure 18.

The chart, Figure 19, summarizes the work of the project.

30

Fig. 13 The Ro-Tap
31

Fig. 14 The Mixer and Powder Measure

12

U. S. NAVAL POSTGRADUATE SCHOOL

Explosives Laboratory

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Run No

1

2

3

4

5

6

7

8

9
10
11
12
13
H

15
16
17
18
19
20
21
22
23
24

Date Sample

12/29/55 TNT CP Powdered
it it ii ti it it

tt it n ti it it

1/4/56
•1/4/56
1/4/56
1/11/56
1/11/56
1/11/56
1/16/56
1/18/56
3/02/56
3/13/56
3/14/56
3/14/56
3/15/56
3/15/56
3/15/56
3/16/56
3/20/56
3/20/56
3/20/56
3/28/56
3/28/56

it ii

TNB CP Powdered

TNB CP Ground thru 120 screen

TNT CP Powdered

50$ TNB(T 120)-50$ chalk

75$ TNB(T 12)-25$ chalk

TNT CP Ground thru 120 screen

87$ TNB -13* chalk

66.7* TNB -33.3$ chalk

50$ TNT(T 120)-50$ chalk

75$ TNT(T 120)-25$ chalk

60$ TNB(T 120)-40$ chalk

40$ TNB(T 120) 60$ chalk

35$ TNT(T 120) 65$ chalk

50$ TNB(T 120)-50$ TNT(T 120)

Size

FPP

OSD

Remarks

6 mg

119.5cm

13cm

13.5mg

81.5

10

33

64.5

7

60

82.5

8

13

83.5

10

7

122

19

36

73

5

56

97

3

38

82.5

7

Repeat of 7

40

81.5

10

Repeat of 9

23

67.5

7

23

61

5.5

21

59

4.5

23

-

-

No expl. to
150 cm

23

116

8

23

52

4

23

69

17

23'

95

4

23

97

11

23

66

1

23

138

23

-

-

-

Not run

23

56

8

23

46

9

37

Run No Date <?„„, t

^^ ^ l» OSD Remarks

25 3/29/56 75% TNB(T 120)-25* TNT(T 120) 23 45 - 8

26 3/29/56 25$ TNB(T 120)-75* TNT(T 120) 23 47 ?

27 3/30/56 90S TOB(T 120)-1Q# TNT(T 120) 23

53 11

38